Sliding bearing

ABSTRACT

A sliding bearing ( 1 ) includes an upper casing ( 3 ) which is made of polyacetal resin as a synthetic resin, has an annular surface ( 2 ), and serves as a first bearing body; a second bearing body ( 5 ) which is made of a synthetic resin, is superposed on the upper casing ( 3 ) so as to be rotatable about an axis ( 0 ), and has an synthetic resin-made annular surface ( 4 ) opposed to the annular surface ( 2 ); and a synthetic resin-made annular sheet ( 6 ) which is interposed between the annular surfaces ( 2 ) and ( 4 ) and slidably abuts against at least one of the upper casing ( 3 ) and the bearing body ( 5 ).

TECHNICAL FIELD

The present invention relates to a sliding bearing, and moreparticularly to a synthetic resin-made sliding bearing which is suitablyincorporated as a thrust sliding bearing of a strut-type suspension(Macpherson type) in a four-wheeled vehicle.

BACKGROUND ART

In general, a strut-type suspension is mainly used in a front wheel of afour-wheeled vehicle, and is constructed such that a strut assemblyincorporating a hydraulic shock absorber in a outer cylinder formedintegrally with a main shaft is combined with a coil spring. Among suchsuspensions, there is a type of structure in which the axis of the coilspring is actively offset with respect to the axis of the strut, so asto allow the sliding of a piston rod of the shock absorber incorporatedin the strut to be effected smoothly. There is another type of structurein which the coil spring is disposed by aligning the axis of the coilspring with the axis of the strut. In either structure, a thrust bearingis disposed between a mounting member of a vehicle body and an upperspring seat of the coil spring to allow the rotation to be effectedsmoothly when the strut assembly rotates together with the coil springby the steering operation.

In this thrust bearing, a rolling bearing using balls or needles or asynthetic resin-made sliding bearing is used. However, the rollingbearing has a possibility that fatigue failure occurs in the balls orneedles due to fine vibrations and vibration load or the like, and thereis a problem in that it is difficult to maintain smooth steeringoperation. The sliding bearing has problems in that since its frictiontorque is high as compared with the rolling bearing, an increase in thethrust load results in an increase in the friction torque, which rendersthe steering operation heavy, and that, depending on a combination ofsynthetic resins, the stick-slip phenomenon occurs, frequently producingfrictional noise attributable to the stick-slip phenomenon.

In addition, a lubricant such as grease is applied to the slidingbearing, and the above-described frictional noise practically does notoccur insofar as such a lubricant is present, as desired, on the slidingsurface. However, there can be cases where the frictional noise beginsto be produced due to the dissipation or the like of the lubricant overlong periods of use.

In addition, since the sliding bearing is generally constructed byincluding two bearing bodies which are superposed on each other, thereis a problem, among others, in that in a case where required frictioncharacteristics cannot be obtained between the two bearing bodies, thedesign or fabrication of these two bearing bodies must be carried outagain.

It should be noted that the above-described problems do not necessarilyoccur only in the thrust sliding bearing incorporated in the strut-typesuspension, but can similarly occur in general sliding bearings.

The present invention has been devised in view of the above-describedaspects, and its object is to provide a sliding bearing in which even ifthe thrust load increases, the friction torque practically does notchange to make it possible to form the sliding surface with a lowfriction torque and maintain such a low coefficient of friction overlong periods of use, which is free of the occurrence of frictional noiseat the sliding surface, which makes it possible to easily adjust thecoefficient of friction to obtain an optimum coefficient of friction,and which, when incorporated into the strut-type suspension as a thrustsliding bearing, makes it possible to ensure smooth steering operationequivalent to that of the rolling bearing, and is capable of readilyadjusting the coefficient of friction optimally so as to make itpossible to eliminate the flutter phenomenon of a steering wheel.

DISCLOSURE OF THE INVENTION

A sliding bearing in accordance with the invention comprises: a firstbearing body having an annular surface; a second bearing body which issuperposed on the first bearing body so as to be rotatable about an axisof the first bearing body, and has an annular surface opposed to theannular surface of the first bearing body; and a synthetic resin-madeannular sheet which is interposed between the annular surfaces andslidably abuts against at least one of the bearing bodies.

According to the sliding bearing in accordance with the invention, sincethe synthetic resin-made annular sheet, which slidably abuts against atleast one of the bearing bodies, is interposed between the annularsurfaces, by merely replacing such a sheet, the coefficient of frictionbetween the first bearing body and the second bearing body can be easilyadjusted to obtain an optimum coefficient of friction. Further, when thesliding bearing is incorporated into the strut-type suspension as athrust sliding bearing, smooth steering operation equivalent to that ofthe rolling bearing can be ensured, and the coefficient of friction canreadily be adjusted optimally so as to make it possible to eliminate theflutter phenomenon of the steering wheel.

The annular sheet is preferably formed of a synthetic resin including atleast one of polyamide resin, polyester resin, polyolefin resin,polycarbonate resin, and fluororesin, and preferably has a thickness offrom 0.05 mm to 1.0 mm.

Both of the bearing bodies are preferably formed of a synthetic resin.Specifically, both of the bearing bodies are preferably formed of asynthetic resin including at least one of polyacetal resin, polyamideresin, polyester resin, polyolefin resin, polycarbonate resin, andfluororesin. More preferably, the first bearing body is formed ofpolyacetal resin, and the second bearing body is formed of a syntheticresin including at least one of polyacetal resin, polyamide resin,polyolefin resin, and fluororesin.

Preferably, the first bearing body at a radially outer peripheral edgeportion thereof is adapted to be resiliently fitted to the secondbearing body at a radially outer peripheral edge portion of the secondbearing body. In addition, a labyrinth is formed between the bearingbodies in at least one of the outer peripheral edge portions and innerperipheral edge portions, as viewed in a radial direction, of both ofthe bearing bodies. By virtue of such a labyrinth, it becomes possibleto satisfactorily prevent the entry of dust, muddy water, and the likeonto a sliding surface between the first bearing body and the secondbearing body.

The second bearing body has a projection formed integrally on theannular surface thereof, and the sheet is interposed between theprojection and the annular surface of the first bearing body andslidably abuts against at least one of the projection and the annularsurface of the first bearing body. With the sliding bearing includingthe second bearing body having such projection, a closed recesssurrounded by the projection is formed on the annular surface of thesecond bearing body, and a fluid is adapted to be filled in at least oneof the closed recess and an annular closed space between the annularsheet and the annular surface of the first bearing body andcorresponding to the closed recess.

According to this sliding bearing, it also becomes possible for thethrust load to be received in a shared manner by the fluid filled in atleast one of the closed recess and the closed space. As a result, thesliding surface of the second bearing body with respect to the annularsurface of the first bearing body can be formed by the surface of thefluid filled in at least one of the closed recess and the closed space.Thus, the sliding bearing has an extremely low coefficient of frictiondue to the contact surface of the fluid. Accordingly, the relativerotation of the second bearing body about the axis of the first bearingbody with respect to the first bearing body can be effected with anextremely low frictional resistance even under the thrust load.Moreover, since such the fluid is filled in at least one of the closedrecess and the closed space sealed by the sheet which is capable offunctioning also as a seal member, it is possible to maintain theaforementioned low coefficient of friction over long periods of use, andeliminate the occurrence of frictional noise at the sliding surface.Also, even when the sliding bearing is incorporated in the strut-typesuspension, it is possible to ensure smooth steering operationequivalent to that of the rolling bearing.

Accordingly, it suffices if the fluid filled in at least one of theclosed recess and the closed space is adapted to receive a thrust load.

The projection is preferably adapted to be flexurally deformed under athrust load so as to make small at least one of a fluid filling capacityof the closed recess and a fluid filling capacity of the closed space.More specifically, the projection is adapted to be flexurally deformedunder a thrust load so as to cause the fluid in at least one of theclosed recess and the closed space to generate internal pressure bymaking small at least one of the fluid filling capacity of the closedrecess and the fluid filling capacity of the closed space.

The fluid which is filled in at least one of the closed recess and theclosed space includes at least one of grease and lubricating oil, and ismore preferably constituted by silicone-based grease.

The projection in a preferred example includes at least an inner annularprojection disposed on an inner peripheral side and an outer annularprojection disposed radially outwardly of and substantiallyconcentrically with the inner annular projection. In another preferredexample, the projection includes at least an inner annular projectiondisposed on an inner peripheral side, an outer annular projectiondisposed radially outwardly of and substantially concentrically with theinner annular projection, and a radial protrusion extending radially andconnected integrally to respective ones of the inner annular projectionand the outer annular projection.

The projection may further include at least one intermediate annularprojection disposed between and substantially concentrically with theinner annular projection and the outer annular projection, as viewed inthe radial direction. If the projection includes such an intermediateannular projection in addition to the inner annular projection and theouter annular projection, even if an unbalanced load is applied to thatsliding bearing in the thrust direction, it is possible to reduce unevendeflection of the inner annular projection and the outer annularprojection. Furthermore, it is possible to favorably hold the closedstate (hermetically sealed state) of the closed recess or the closedspace. Thus, the reception of the thrust load by the fluid can bemaintained over long periods of time without leakage of the fluid fromthe closed recess or the closed space.

In the present invention, the second bearing body may be formed of anintegrated one-piece member, but alternatively may include a bearingmember and an annular piece disposed between the bearing member and thefirst bearing body so as to be rotatable about the axis of the firstbearing body with respect to at least one of the first bearing body andthe bearing member. Here, the annular piece has the annular surfaceopposing the synthetic resin-made annular surface of the first bearingbody as well as the projection formed integrally on the annular surface.It should be noted that the second bearing body in accordance with theinvention may be formed by the bearing member and the annular piece nothaving the projection.

In the second bearing body having two members including the bearingmember and the annular piece, preferably, the bearing member is formedof polyacetal resin, and the annular piece is formed of a syntheticresin including at least one of polyamide resin, polyolefin resin, andfluororesin.

Preferably, the annular piece has another annular surface disposedoppositely to the annular surface opposing the annular surface of thefirst bearing body as well as other projection formed integrally on theother annular surface, and the bearing member has a synthetic resin-madeannular surface opposing the other annular surface of the annular pieceand slidably abutting against the other projection. Alternatively, thesecond bearing body in accordance with the invention may be formed bythe bearing member and the annular piece not having the projection.

In the case where the second bearing body in accordance with theinvention is formed by the bearing member and the annular piece nothaving the projection, the annular surface of the bearing member may bedirectly abutted against the other annular surface of the annular piece.Alternatively, however, another annular sheet may be interposed betweenthe annular surface of the bearing member and the other annular surfaceof the annular piece. In addition, in the case where the annular piecehas the other projection, a synthetic resin-made other annular sheet maybe interposed between the annular surface of the bearing member and theother projection, and the other annular sheet may slidably abut againstat least one of the annular surface of the bearing member and the otherprojection.

In the same way as the aforementioned sheet, the other annular sheet maybe formed of a synthetic resin including at least one of polyamideresin, polyester resin, polyolefin resin, polycarbonate resin, andfluororesin, and may have a thickness of from 0.05 mm to 1.0 mm.

Another closed recess surrounded by the other projection may be formedon the other annular surface of the annular piece, and another fluid maybe adapted to be filled in at least one of the other closed recess andanother annular closed space formed between the annular surface of thebearing member and the other annular sheet corresponding to the otherclosed recess. Preferably, the other fluid filled in the other closedrecess and the other closed space is adapted to receive a thrust load.More preferably, the other projection is adapted to be flexurallydeformed under a thrust load so as to make small at least one of a fluidfilling capacity of the other closed recess and a fluid filling capacityof the other closed space. In addition, the other projection may beadapted to be flexurally deformed under a thrust load so as to cause theother fluid in at least one of the other closed recess and the otherclosed space to generate internal pressure by making small at least oneof the fluid filling capacity of the other closed recess and the fluidfilling capacity of the other closed space.

Preferably, the other fluid also includes at least one of grease andlubricating oil, and is more preferably constituted by silicone-basedgrease.

In the same way as the aforementioned projection, the other projectionmay include at least other inner annular projection disposed on an innerperipheral side and other outer annular projection disposed radiallyoutwardly of and substantially concentrically with the other innerannular projection, or may include at least other inner annularprojection disposed on an inner peripheral side, other outer annularprojection disposed radially outwardly of and substantiallyconcentrically with the other inner annular projection, and other radialprotrusion extending radially and connected integrally to respectiveones of the other inner annular projection and the other outer annularprojection.

The other projection may further include at least one other intermediateannular projection disposed between and substantially concentricallywith the other inner annular projection and the other outer annularprojection, as viewed in the radial direction. If the other projectionincludes such another intermediate annular projection in addition to theother inner annular projection and the other outer annular projection,even if an unbalanced load is applied to that sliding bearing in thethrust direction, it is possible to reduce uneven deflection of theother inner annular projection and the other outer annular projection.Furthermore, it is possible to favorably hold the closed state(hermetically sealed state) of the other closed recess or the otherclosed space. Thus, the reception of the thrust load by the other fluidcan be maintained over long periods of time without leakage of the otherfluid from the other closed recess or the other closed space.

In the present invention, the first and the second bearing bodies mayrespectively have mutually opposing cylindrical surfaces. In this case,a synthetic resin-made cylindrical sheet may be interposed between bothcylindrical surfaces, and the cylindrical sheet may slidably abutagainst at least one of both cylindrical surfaces.

Preferably, in the same way as the aforementioned sheet, the cylindricalsheet may also be formed of a synthetic resin including at least one ofpolyamide resin, polyester resin, polyolefin resin, polycarbonate resin,and fluororesin, and may have a thickness of from 0.05 mm to 1.0 mm.

Preferably, the sliding bearing in accordance with the present inventionis for use as a thrust sliding bearing of a strut-type suspension in afour-wheeled vehicle. However, the present invention is not limited tothe same, and the sliding bearing in accordance with the presentinvention may be used for other types.

Preferably, the sliding bearing in accordance with the present inventionis for use as a thrust sliding bearing of a strut-type suspension in afour-wheeled vehicle. Here, the first bearing body may be the uppercasing or the lower casing, while the second bearing body may be thelower casing or the upper casing. The first bearing body may be theupper casing, while the second bearing body may be constituted by thebearing piece and the lower casing. Further, the first bearing body maybe constituted by the lower casing, while the second bearing body may bethe bearing piece and the upper casing.

According to the present invention, it is possible to provide asynthetic resin-made sliding bearing in which even if the thrust loadincreases, the friction torque practically does not change to make itpossible to form the sliding surface with a low friction torque andmaintain such a low coefficient of friction over long periods of use,which is free of the occurrence of frictional noise at the slidingsurface, which makes it possible to easily adjust the coefficient offriction to obtain an optimum coefficient of friction, and which, whenincorporated into the strut-type suspension as a thrust sliding bearing,makes it possible to ensure smooth steering operation equivalent to thatof the rolling bearing, and is capable of readily adjusting thecoefficient of friction optimally so as to make it possible to eliminatethe flutter phenomenon of the steering wheel.

Hereafter, a description will be given of the present invention and themode for carrying out the invention with reference to the preferredembodiments shown in the drawings. It should be noted that the presentinvention is not limited to these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a preferred embodiment of theinvention;

FIG. 2 is a plan view of an annular piece in accordance with theembodiment shown in FIG. 1;

FIG. 3 is a plan view of a sheet of the embodiment shown in FIG. 1;

FIG. 4 is an explanatory diagram of an example in which the embodimentshown in FIG. 1 is incorporated in a strut-type suspension;

FIG. 5 is a fragmentary cross-sectional view of another preferredembodiment of the invention;

FIG. 6 is a fragmentary cross-sectional view of still another preferredembodiment of the invention;

FIG. 7 is a fragmentary cross-sectional view of a further preferredembodiment of the invention;

FIG. 8 is a fragmentary cross-sectional view of a still furtherpreferred embodiment of the invention;

FIG. 9 is a fragmentary cross-sectional view of a further preferredembodiment of the invention;

FIG. 10 is a fragmentary cross-sectional view of a still furtherpreferred embodiment of the invention;

FIG. 11 is a fragmentary cross-sectional view of a further preferredembodiment of the invention;

FIG. 12 is a cross-sectional view of a further preferred embodiment ofthe invention;

FIG. 13 is a cross-sectional view of a further preferred embodiment ofthe invention;

FIG. 14 is a perspective view of a radial bearing body and a sheet ofthe embodiment shown in FIG. 13;

FIG. 15 is a plan view of another example of the annular piece inaccordance with the invention;

FIG. 16 is a plan view of still another example of the annular piece inaccordance with the invention;

FIG. 17 is a cross-sectional view of a further preferred embodiment ofthe invention; and

FIG. 18 is a plan view of the annular piece of the embodiment shown inFIG. 17.

EMBODIMENTS

In FIGS. 1 to 3, a sliding bearing 1 for use in a strut-type suspensionin a four-wheeled vehicle in accordance with this embodiment iscomprised of an upper casing 3 having an annular surface 2, which ismade of polyacetal resin as a synthetic resin, and serves as a firstbearing body; a second bearing body 5 which is superposed on the uppercasing 3 so as to be rotatable about an axis O of the upper casing 3 inan R direction, and has an annular surface 4 made of a synthetic resinand opposed to the annular surface 2 of the upper casing 3; and asynthetic resin-made annular sheet 6 which is interposed between theannular surfaces 2 and 4 and slidably abuts against at least one of theupper casing 3 and the bearing body 5, i.e., against both of the uppercasing 3 and the bearing body 5 in this embodiment.

The synthetic resin-made upper casing 3 is formed integrally with andincludes an annular upper casing body portion 13 having the annularsurface 2 and an inner peripheral surface 12 for defining a circularhole 11 in a central portion; an innermost peripheral-side cylindricalsuspended portion 14 formed integrally with a radially inner peripheraledge of the upper casing body portion 13 and suspended toward thebearing body 5; an inner peripheral-side cylindrical suspended portion15 disposed radially outwardly of the innermost peripheral-sidecylindrical suspended portion 14, formed integrally with the annularsurface 2, and suspended toward the bearing body 5; a cylindricalsuspended engaging portion 16 formed integrally with a radially outerperipheral edge of the upper casing body portion 13; an outerperipheral-side cylindrical suspended portion 17 disposed radiallyinwardly of the cylindrical suspended engaging portion 16 and radiallyoutwardly of the inner peripheral-side cylindrical suspended portion 15,and formed integrally with the annular surface 2; and an engaging hookportion 18 formed on a radially inner peripheral surface of thecylindrical suspended engaging portion 16.

The bearing body 5 has a projection formed integrally with the annularsurface 4 and including an inner annular projection 19 disposed on aninner peripheral side and an outer annular projection 20 disposedradially outwardly of and substantially concentrically with the innerannular projection 19. The bearing body 5 includes a polyacetalresin-made lower casing 21 serving as a bearing member; and an annularpiece 22 which is disposed between the lower casing 21 and the uppercasing 3 rotatably about the axis O of the upper casing 3 with respectto at least one, both in this embodiment, of the upper casing 3 and thelower casing 21, and which is formed of a synthetic resin, preferably asynthetic resin including at least one of polyamide resin, polyolefinresin, and fluororesin.

The synthetic resin-made lower casing 21 is formed integrally andincludes the following: an annular lower casing body portion 32 havingan inner peripheral surface 30 and an annular surface 31; an innermostperipheral-side cylindrical protruding portion 33 formed integrally witha radially inner peripheral edge of the lower casing body portion 32 andprotruding toward the upper casing 3 so as to be disposed between theinnermost peripheral-side cylindrical suspended portion 14 and the innerperipheral-side cylindrical suspended portion 15; an innerperipheral-side cylindrical protruding portion 34 disposed radiallyoutwardly of the innermost peripheral-side cylindrical protrudingportion 33, formed integrally with the annular surface 31, andprotruding toward the upper casing 3; a cylindrical protruding engagingportion 35 formed integrally with a radially outer peripheral edge ofthe lower casing body portion 32 and protruding toward the upper casing3 so as to be disposed between the cylindrical suspended engagingportion 16 and the outer peripheral-side cylindrical suspended portion17; an outer peripheral-side cylindrical protruding portion 36 disposedradially inwardly of the cylindrical protruding engaging portion 35 andradially outwardly of the inner peripheral-side cylindrical protrudingportion 34, formed integrally with the annular surface 31, andprotruding toward the upper casing 3; an engaging hook portion 37 formedon a radial outer peripheral surface of the cylindrical protrudingengaging portion 35 and adapted to engage the engaging hook portion 18;and a cylindrical portion 40 formed integrally with an outer surface 38of the lower casing body portion 32 on a radially inner peripheral sideof the lower casing body portion 32, having an inner peripheral surface39 continuing to the inner peripheral surface 30, and protrudingdownward. A circular hole 41 in a central portion of the lower casingbody portion 32, which is substantially concentric with the circularhole 11, is defined by the inner peripheral surface 30 and the innerperipheral surface 39.

The innermost peripheral-side cylindrical protruding portion 33 isformed such that its height H1 from the annular surface 31 is lower thanthe height H2 of the inner peripheral-side cylindrical protrudingportion 34 similarly from the annular surface 31. Likewise, thecylindrical protruding engaging portion 35 is formed such that itsheight H3 from the annular-surface 31 is lower than the height H4 of theouter peripheral-side cylindrical protruding portion 36 similarly fromthe annular surface 31 (see FIG. 5). It should be noted that the presentinvention is not limited to the same, and, for example, the innermostperipheral-side cylindrical protruding portion 33 and the innerperipheral-side cylindrical protruding portion 34 may be set to be atthe same height (H1=H2) and the cylindrical protruding engaging portion35 and the outer peripheral-side cylindrical protruding portion 36 maybe set at the same height (H3=H4).

In addition to the annular surface 4 opposing the annular surface 2 andthe inner annular projection 19 and the outer annular projection 20formed integrally with the annular surface 4, the annular piece 22 hasanother annular surface 55 disposed oppositely to the annular surface 4as well as other projection including an inner annular projection 56disposed on the inner peripheral side and an outer annular projection 57disposed radially outwardly of and substantially concentrically with theinner annular projection 56 and formed integrally with annular surface55. The synthetic resin-made annular surface 31 of the lower casing 21opposing the annular surface 55 of the annular piece 22 slidably abutsagainst the inner annular projection 56 and the outer annular projection57 which are formed in the same way as the inner annular projection 19and the outer annular projection 20.

An annular closed recess 58 surrounded by the inner annular projection19 and the outer annular projection 20 is formed on the annular surface4, while an annular closed recess 59 surrounded by the inner annularprojection 56 and the outer annular projection 57 is formed on theannular surface 55. The closed recesses 58 and 59 are fully filled withfluids 60 and 61 constituted by at least one of grease and lubricatingoil, preferably silicone-based grease.

The sheet 6, which is formed of a synthetic resin, preferably asynthetic resin including at least one of polyamide resin, polyesterresin, polyolefin resin, polycarbonate resin, and fluororesin and has athickness of from 0.05 mm to 1.0 mm, is interposed between the annularsurface 2 and the projection including the inner annular projection 19and the outer annular projection 20, and slidably abuts against at leastone of the annular surface 2 and the projection including the innerannular projection 19 and the outer annular projection 20, i.e., againstboth of them in this embodiment.

The closed recess 58 is surrounded by the inner annular projection 19and the outer annular projection 20 such that its area opposing thesheet 6 is greater than the total area of the inner annular projection19 and the outer annular projection 20 which slidably abut against thesheet 6. In other words, the closed recess 58 is surrounded by the innerannular projection 19 and the outer annular projection 20 such that thearea of the fluid 60 contacting the sheet 6 is greater than the totalarea of the inner annular projection 19 and the outer annular projection20 which slidably abut against the sheet 6. The closed recess 59 issurrounded by the inner annular projection 56 and the outer annularprojection 57 such that its area opposing the annular surface 31 isgreater than the total area of the inner annular projection 56 and theouter annular projection 57 which slidably abut against the annularsurface 31. In other words, the closed recess 59 is surrounded by theinner annular projection 56 and the outer annular projection 57 suchthat the area of the fluid 61 contacting the annular surface 31 isgreater than the total area of the inner annular projection 56 and theouter annular projection 57 which slidably abut against the annularsurface 31.

Under a thrust load, the inner annular projection 19 and the outerannular projection 20 are adapted to abut against the sheet 6 in such amanner as to be flexurally deformed, so as to cause the fluid 60 in theclosed recess 58 to generate internal pressure by making the fluidfilling capacity of the closed recess 58 small. Under a thrust load, theinner annular projection 56 and the outer annular projection 57 are alsoadapted to abut against the annular surface 31 in such a manner as to beflexurally deformed, so as to cause the fluid 61 in the closed recess 59to generate internal pressure by making the fluid filling capacity ofthe closed recess 59 small.

The upper casing 3 at the engaging hook portion 18 of the cylindricalsuspended engaging portion 16 of its radially outer peripheral edgeportion is adapted to be resiliently fitted and secured to the lowercasing 21 by being resiliently engaged in a snap-fit fashion with theengaging hook portion 37 of the cylindrical protruding engaging portion35 of the radially outer peripheral edge portion in the lower casing 21.

In at least one portions of the radially outer peripheral edge portionsand inner peripheral edge portions of the upper casing 3 and the lowercasing 21, i.e., both peripheral edge portions in this embodiment, alabyrinth 65 is arranged to be formed between the upper casing 3 and thelower casing 21 by the upper casing body portion 13, the cylindricalsuspended engaging portion 16, and the outer peripheral-side cylindricalsuspended portion 17, as well as the lower casing body portion 32, thecylindrical protruding engaging portion 35, and the outerperipheral-side cylindrical protruding portion 36. A labyrinth 66 isarranged to be formed by the upper casing body portion 13, the innermostperipheral-side cylindrical suspended portion 14, and the innerperipheral-side cylindrical suspended portion 15, as well as the lowercasing body portion 32, the innermost peripheral-side cylindricalprotruding portion 33, and the inner peripheral-side cylindricalprotruding portion 34. Entry of dust, muddy water, and the like from theoutside into the closed recesses 58 and 59 is prevented by such alabyrinth 65 at the outer peripheral edge portion and such a labyrinth66 at the inner peripheral edge portion.

The above-described sliding bearing 1 is used by being fitted between anupper spring seat 72 of a coil spring 71 in a strut-type suspensionassembly on the one hand, and a mounting member 74 on the vehicle bodyside to which a piston rod 73 of a hydraulic damper is secured on theother hand, as shown in FIG. 4. In this case, an upper portion of thepiston rod 73 is inserted in the circular holes 11 and 41 so as to berotatable about the axis O in the R direction with respect to the uppercasing 3 and the lower casing 21.

In the strut-type suspension assembly installed by means of the slidingbearing 1, as shown in FIG. 4, at the time of the steering operation,the relative rotation of the upper spring seat 72 about the axis O inthe R direction by means of the coil spring 71 is smoothly effected bythe relative rotation of the lower casing 21 in the same direction withrespect to the upper casing 3.

Then, according to the sliding bearing 1, the synthetic resin-madeannular sheet 6, which slidably abuts against the upper casing bodyportion 13 of the upper casing 3 and the inner annular projection 19 andthe outer annular projection 20 of the annular piece 22, is interposedbetween the annular surfaces 2 and 4. Therefore, by merely replacingsuch a sheet 6, the coefficient of friction between the upper casing 3and the annular piece 22 can be easily adjusted to obtain an optimumcoefficient of friction. Further, when the sliding bearing 1 isincorporated into the strut-type suspension as a thrust sliding bearing,smooth steering operation equivalent to that of the rolling bearing canbe ensured, and the coefficient of friction can readily be adjustedoptimally so as to make it possible to eliminate the flutter phenomenonof the steering wheel.

In addition, according to the sliding bearing 1, the closed recess 58,which is surrounded by the inner annular projection 19 and the outerannular projection 20 slidably abutting against the sheet 6, is formedon the annular surface 4, and the fluid 60 constituted by silicone-basedgrease is arranged to be filled in such a closed recess 58. At the sametime, under a thrust load, the inner annular projection 19 and the outerannular projection 20 are adapted to abut against the sheet 6 in such amanner as to be flexurally deformed, so as to cause the fluid 60 in theclosed recess 58 to generate internal pressure by making the fluidfilling capacity of the closed recess 58 small. As a result, the thrustload can also be received in a shared manner by the fluid 60 filled inthe closed recess 58. In other words, the sliding surface of the lowercasing 21 with respect to the sheet 6 is constituted by the surfaces ofthe inner annular projection 19 and the outer annular projection 20contacting the sheet 6, as well as the surface of the fluid 60 filled inthe closed recess 58 and contacting the sheet 6.

In addition, according to the sliding bearing 1, since the area of thesurface of the fluid 60 filled in the closed recess 58 and contactingthe sheet 6 is set to be greater than the total area of the innerannular projection 19 and the outer annular projection 20 which slidablyabut against the sheet 6, the thrust load borne by the inner annularprojection 19 and the outer annular projection 20 decreasessubstantially. Hence, the frictional resistance between the innerannular projection 19 and the outer annular projection 20 on the onehand, and the sheet 6 on the other hand, is substantially reduced. Atthe same time, since the frictional resistance due to the surface of thefluid 60 contacting the sheet 6 is extremely small, an extremely lowfrictional resistance is obtained as a whole. Accordingly, the relativerotation of the lower casing 21 about the axis O of the upper casing 3in the R direction with respect to the upper casing 3 can be effectedwith an extremely low frictional resistance even under the thrust load.Moreover, since such a fluid 60 is filled in the closed recess 58 sealedby the sheet 6 which is capable of functioning as a seal member, it ispossible to maintain a low coefficient of friction over long periods ofuse, and eliminate the occurrence of frictional noise at the slidingsurface. Also, even when the sliding bearing 1 is incorporated in thestrut-type suspension, it is possible to ensure smooth steeringoperation equivalent to that of the rolling bearing.

With the sliding bearing 1, the closed recess 59 is also filled with thefluid 61, and the inner annular projection 56 and the outer annularprojection 57 under a thrust load are adapted to abut against theannular surface 31 in such a manner as to be flexurally deformed, so asto cause the fluid 61 in the closed recess 59 to generate internalpressure by making the fluid filling capacity of the closed recess 59small. Therefore, even if the frictional resistance between the innerannular projection 19 and the outer annular projection 20 on the onehand, and the sheet 6 on the other hand, becomes large for some cause orother, it is possible to ensure sliding with an extremely lowcoefficient of friction between the inner annular projection 56 and theouter annular projection 57 on the one hand, and the annular surface 31on the other hand, in the same way as described above. Thus, therelative rotation of the lower casing 21 about the axis O of the uppercasing 3 in the R direction with respect to the upper casing 3 can beeffected with an extremely low frictional resistance even under thethrust load, so that the sliding bearing 1 becomes failsafe.

In the above description, the sheet 6 is interposed between the annularsurface 2 and the projection comprising the inner annular projection 19and the outer annular projection 20 by being lined closely to theannular surface 2. Alternatively, as shown in FIG. 5, the sheet 6 may beinterposed between the annular surface 2 and the projection includingthe inner annular projection 19 and the outer annular projection 20 bybeing lined closely to the annular surface 4, such that an annularclosed space 81 corresponding to the closed recess 58 is formed betweenthe sheet 6 and the annular surface 2. In this case, it suffices if theclosed space 81 is fully filled with the fluid 60 to receive the thrustload by the fluid 60 filled in the closed space 81, in the same way asdescribed above. In addition, instead of lining the sheet 6 closely tothe annular surface 2 or 4, the sheet 6 may be deflected such that boththe closed recess 58 and the closed space 81 are formed between theannular surface 2 and the annular surface 4, and both the closed recess58 and the closed space 81 may be fully filled with the fluid 60.

In addition, with the above-described sliding bearing 1, although theannular piece 22 having the inner annular projection 56 and the outerannular projection 57 on its annular surface 55 is used, the slidingbearing 1 may alternatively be constructed by using the annular piece 22having the flat annular surface 55 without providing the inner annularprojection 56 and the outer annular projection 57, and by causing theannular surface 55 to slidably abut against the flat annular surface 31of the lower casing body portion 32, as shown in FIG. 6. Further,instead of constructing the bearing body 5 by the lower casing 21 andthe separate annular piece 22 in the above-described manner, an annularcentral protruding portion 82 equivalent to the annular piece 22 may beformed integrally with the lower casing body portion 32, as shown inFIG. 7, and the projection comprising the inner annular projection 19and the outer annular projection 20 may be formed integrally with theannular surface 4 of the annular central protruding portion 82, to causethe projection including the inner annular projection 19 and the outerannular projection 20 to slidably abut against the sheet 6. In thiscase, as shown in FIG. 7, the inner peripheral-side cylindricalprotruding portion 34 and the outer peripheral-side cylindricalprotruding portion 36 may be integrated with the annular centralprotruding portion 82. Alternatively, the annular central protrudingportion 82 may be formed integrally with the lower casing body portion32 by creating a radial gap between the inner peripheral-sidecylindrical protruding portion 34 and the outer peripheral-sidecylindrical protruding portion 36, or the annular central protrudingportion 82 may be formed integrally with the lower casing body portion32 by omitting the inner peripheral-side cylindrical protruding portion34 and the outer peripheral-side cylindrical protruding portion 36.

In addition, although with the above-described sliding bearing 1 thesheet 6 is interposed between the annular surfaces 2 and 4,alternatively, the sheet 6 may be interposed between the annular surface31 and the annular surface 55, as shown in FIGS. 8 to 10, to allow thesheet 6 to slidably abut against both the annular surface 31 and theprojection comprising the inner annular projection 56 and the outerannular projection 57. Here, the projection including the inner annularprojection 19 and the outer annular projection 20 of the annular piece22 may be slidably abutted against the annular surface 2, as shown inFIG. 8. Alternatively, the flat annular surface 4 of the annular piece22 may be slidably abutted against the annular surface 2, as shown inFIG. 9. Still alternatively, as shown in FIG. 10, the upper casing 3 maybe constructed by an annular central protruding portion 83 which isformed integrally with the upper casing body portion 13 and which isequivalent to the annular piece 22 and is similar to the annular centralprotruding portion 82. In either case, it suffices if the closed recess59 is fully filled with the fluid 61 constituted by silicone-basedgrease. Furthermore, a closed space equivalent to the closed space 81may be formed between the annular surface 31 and the annular surface 55,and such a closed space may be fully filled with the fluid 61constituted by silicone-based grease or the like in the same way asdescribed above.

In addition, as shown in FIG. 11, for example, the sheet 6 may beinterposed between the annular surface 2 and the annular surface 4, andanother sheet 6 may be interposed between the annular surface 31 and theannular surface 55. In this case, the sheet 6 may be slidably abuttedagainst the annular surface 2 and the inner annular projection 19 andthe outer annular projection 20, and the synthetic resin-made othersheet 6 may be slidably abutted against the annular surface 31 and theinner annular projection 56 and the outer annular projection 57.However, as shown in FIG. 11, both sheets 6 may be slidably abuttedagainst the flat annular surfaces 4 and 55 respectively by using theannular piece 22 having the flat annular surfaces 4 and 55. Thesynthetic resin-made other sheet 6 is also sufficient if it is formed ofa synthetic resin including at least one of polyamide resin, polyesterresin, polyolefin resin, polycarbonate resin, and fluororesin and has athickness of from 0.05 mm to 1.0 mm.

Incidentally, with the above-described sliding bearing 1, the uppercasing 3 is constructed by integrally forming the innermostperipheral-side cylindrical suspended portion 14 and the innerperipheral-side cylindrical suspended portion 15 on the annular surface2 of the upper casing body portion 13, and the lower casing 21 isconstructed by integrally forming the innermost peripheral-sidecylindrical protruding portion 33 and the inner peripheral-sidecylindrical protruding portion 34 or the like on the annular surface 31of the lower casing body portion 32. Alternatively, however, as shown inFIG. 12, the upper casing 3 may be constructed by including acylindrical portion 91 formed integrally with an annular outer surface90 of the upper casing body portion 13; an annular portion 92 formedintegrally with the cylindrical portion 91; and a cylindrical suspendedportion 93 formed integrally with the annular portion 92. Meanwhile, thelower casing 21 may be constructed by including a cylindrical portion 95formed integrally with the annular surface 31 of the lower casing bodyportion 32 and disposed substantially concentrically with and radiallyinwardly of the cylindrical portion 91; an annular projecting portion 97formed integrally with the annular surface 31 of the lower casing bodyportion 32 and a cylindrical outer surface 96 of the cylindrical portion95; and a cylindrical projecting portion 99 formed integrally with anannular end face 98 of the cylindrical portion 95 and disposed betweenthe cylindrical portion 91 and the cylindrical suspended portion 93.

With the sliding bearing 1 shown in FIG. 12, the labyrinth 66 isarranged to be formed between the upper casing 3 and the lower casing 21by the cylindrical portion 91, the annular portion 92, the cylindricalsuspended portion 93, the cylindrical portion 95, and the cylindricalprojecting portion 99. The arrangement provided is such that an upperportion of the piston rod 73 is inserted into a circular hole 102defined by a cylindrical inner surface 101 of the cylindrical portion 95so as to be rotatable about the axis O in the R direction with respectto the upper casing 3 and the lower casing 21. Further, also with thesliding bearing 1 shown in FIG. 12, the labyrinth 65 is formed betweenthe upper casing 3 and the lower casing 21 by the upper casing bodyportion 13, the cylindrical suspended engaging portion 16, and the outerperipheral-side cylindrical suspended portion 17 and by the lower casingbody portion 32, the cylindrical protruding engaging portion 35, and theouter peripheral-side cylindrical protruding portion 36, and the sheet 6is interposed between, for instance, both annular surfaces 2 and 4, inthe same way as described above.

Furthermore, the upper casing 3 and the lower casing 21 may beconstructed, as shown in FIG. 13. With the sliding bearing 1 shown inFIG. 13, in addition to the above-described upper casing body portion13, cylindrical suspended engaging portion 16, outer peripheral-sidecylindrical suspended portion 17, and engaging hook portion 18, theupper casing 3 includes a suspended cylindrical portion 111 formedintegrally with the annular surface 2 of the upper casing body portion13; a pair of suspended annular portions 113 and 114 which are mutuallysubstantially concentric and formed integrally with an end face 112 ofthe suspended cylindrical portion 111; and a cylindrical portion 116formed integrally with the annular surface 2 of the upper casing bodyportion 13 and a radially outer cylindrical surface 115 of the suspendedcylindrical portion 111. Meanwhile, in addition to the above-describedlower casing body portion 32, inner peripheral-side cylindricalprotruding portion 34, cylindrical protruding engaging portion 35, outerperipheral-side cylindrical protruding portion 36, and engaging hookportion 37, the lower casing 21 includes a cylindrical portion 121disposed on a radially inner peripheral side of the lower casing bodyportion 32 and formed integrally with the outer surface 38 of the lowercasing body portion 32; a hollow truncated cone portion 122 formedintegrally with an end face of the cylindrical portion 121 by forming anannular stepped portion 126; an annular portion 123 formed integrally onan inner peripheral surface of the truncated cone portion 122; and acylindrical projecting portion 125 formed integrally with an annularsurface 124 of the annular portion 123 and disposed between the pair ofsuspended annular portions 113 and 114.

With the sliding bearing 1 shown in FIG. 13, in addition to thelabyrinth 65 which is similar to the above-described one, the labyrinth66 is formed between the upper casing 3 and the lower casing 21 by thesuspended cylindrical portion 111, the pair of suspended annularportions 113 and 114, the annular portion 123, and the cylindricalprojecting portion 125, and the sheets 6 are for example respectivelyinterposed between the annular surfaces 2 and 4 and between the annularsurfaces 31 and 55. The arrangement provided is such that the upperportion of the piston rod 73 is inserted into a circular hole 132defined by a cylindrical inner surface 131 of the suspended cylindricalportion 111 so as to be rotatable about the axis O in the R directionwith respect to the upper casing 3 and the lower casing 21.

Incidentally, as in the sliding bearing 1 shown in FIG. 13, acylindrical radial bearing body 145 and a cylindrical sheet 146 may beinterposed between the cylindrical surface 115 on the radially outerside of the suspended cylindrical portion 111 and a cylindrical surface142 on the radially inner side of the cylindrical portion 121 opposingthe cylindrical surface 115. Here, as shown in FIG. 14, the radialbearing body 145 has a cylindrical portion 140; and a plurality ofprojections 148 formed integrally with a cylindrical inner surface 147of the cylindrical portion 140 and extending from one annular end face149 of the cylindrical portion 140 to the other annular end face 150 ofthe cylindrical portion 140. In the same way as the sheet 6, thecylindrical sheet 146 is formed of a synthetic resin including at leastone of polyamide resin, polyester resin, polyolefin resin, polycarbonateresin, and fluororesin and has a thickness of from 0.05 mm to 1.0 mm.The cylindrical sheet 146 is disposed in the radial bearing body 145.The cylindrical sheet 146 at its cylindrical outer surface 161 slidablyabuts against apex surfaces 162 of the plurality of projections 148, andat its cylindrical inner surface 163 slidably abuts against thecylindrical surface 115 of the suspended cylindrical portion 111.

The sliding bearing 1 includes the upper casing 3 and the bearing body 5respectively having the above-described mutually opposing cylindricalsurfaces 115 and 142, the synthetic resin-made cylindrical sheet 146 isinterposed between the cylindrical surfaces 115 and 142 and slidablyabuts against at least one of both cylindrical surfaces 115 and 142,i.e., against the cylindrical surface 115 in this embodiment, and acylindrical outer surface 165 of the cylindrical portion 140 slidablyabuts against the cylindrical surface 142. In this sliding bearing 1,the radial load of the bearing body 5 with respect to the upper casing 3can be received by means of the radial bearing body 145 and thecylindrical sheet 146. Thus, the relative rotation of the lower casing21 about the axis O of the upper casing 3 in the R direction withrespect to the upper casing 3 can be effected with an extremely lowfrictional resistance even under the radial load.

The radial bearing body 145 may be constructed by only the cylindricalportion 140 without providing the plurality of projections 148. Further,the plurality of projections 148 may be formed integrally on the outersurface 165 of the cylindrical portion 140. In this case, it suffices ifthe sheet 146 is disposed on the radially outer side of the radialbearing body 145. Furthermore, the plurality of projections 148 may beformed integrally on both the inner surface 147 and the outer surface165 of the cylindrical portion 140. In any one of the above-describedforms of the radial bearing body 145, the sheets 146 may respectivelydisposed on both the radially outer and inner sides of the radialbearing body 145.

As shown in FIG. 15, the annular piece 22 may be formed by including, inaddition to at least one of the set of the inner annular projection 19and the outer annular projection 20 and the set of the inner annularprojection 56 and the outer annular projection 57, the protrusionsformed integrally with the annular surface 4 (55) and having aplurality-of radial protrusions 151 which are integrally connected tothe inner annular projection 19 (56) and the outer annular projection 20(57), respectively, so as to extend radially and are arranged at equalintervals in the circumferential direction. In the case of the annularpiece 22 shown in FIG. 15, it suffices if a plurality of closed recesses152, which are mutually independent of each other and are surrounded bythe inner annular projection 19 (56) and the outer annular projection 20(57) and by the plurality of radial protrusions 151, are fully filledwith the fluid 60 (61) constituted by silicone-based grease similar tothe above-described one.

Furthermore, instead of forming the annular piece 22 by including theprojection having the inner annular projection 19 (56) and the outerannular projection 20 (57), as shown in FIG. 16, the annular piece 22may be formed by including a protrusion constituted by a plurality ofradial protrusions 171 formed integrally on at least one of the annularsurfaces 4 and 55 and arranged at equal intervals in the circumferentialdirection. In a case where the plurality of radial protrusions 171 areformed on both annular surfaces 4 and 55, it suffices if the pluralityof radial protrusions 171 on the annular surface 4 and the plurality ofradial protrusions 171 on the annular surface 55 are arranged by beingpositionally offset from each other in the circumferential direction.

In addition, as shown in FIGS. 17 and 18, the annular piece 22 may beformed by including, in addition to at least one of the set of the innerannular projection 19 and the outer annular projection 20 and the set ofthe inner annular projection 56 and the outer annular projection 57, atleast one of the projection further having an intermediate annularprojection 181 formed integrally with the annular surface 4 and disposedbetween the inner annular projection 19 and the outer annular projection20 in a radial direction and substantially concentrically with the innerannular projection 19 and the outer annular projection 20, as well asthe other projection further having other intermediate annularprojection 182 formed integrally with the annular surface 55 anddisposed between the inner annular projection 56 and the outer annularprojection 57 in the radial direction and substantially concentricallywith the inner annular projection 56 and the outer annular projection57.

With the sliding bearing 1 using the annular piece 22 shown in FIGS. 17and 18 for the upper casing 3, the sheet 6, and the lower casing 21 ofthe form shown in FIG. 1, the closed recesses 58 are formed by anannular inner closed recess 185 surrounded by the inner annularprojection 19 and the intermediate annular projection 181 and an annularouter closed recess 186 surrounded by the intermediate annularprojection 181 and the outer annular projection 20. Meanwhile, theclosed recesses 59 are formed by an annular inner closed recess 187surrounded by the inner annular projection 56 and the intermediateannular projection 182 and an annular outer closed recess 188 surroundedby the intermediate annular projection 182 and the outer annularprojection 57.

With the sliding bearing 1 using the annular piece 22 shown in FIGS. 17and 18 and including the projection having the intermediate annularprojections 181 and 182 in addition to the inner annular projections 19and 56 and the outer annular projections 20 and 57, even if anunbalanced load is applied to that sliding bearing 1 in the thrustdirection, it is possible to reduce uneven deflection of the innerannular projections 19 and 56 and the outer annular projections 20 and57. Furthermore, it is possible to favorably hold the closed state(hermetically sealed state) of the closed recesses 58 formed by theinner closed recess 185 and the outer closed recess 186 and the closedrecesses 59 formed by the inner closed recess 187 and the outer closedrecess 188. Thus, the reception of the thrust load by the fluids 60 and61 can be maintained over long periods of time without leakage of thefluids 60 and 61 from the closed recesses 58 and 59.

The above-described intermediate annular projections 181 and 182 may beapplied, as required, to the annular piece 22 and the sliding bearing 1of the respective forms shown in FIGS. 5 to 10, and FIGS. 12, 13, and 15in the same way as described above. Furthermore, each of theintermediate annular projections 181 and 182 is not limited to onepiece, and may consist of a plurality of pieces arranged substantiallyconcentrically with each other. In addition, either one of theintermediate annular projections 181 and 182 may be omitted.

1. A sliding bearing comprising: a first bearing body having an annularsurface; a second bearing body which is superposed on said first bearingbody so as to be rotatable about an axis of said first bearing body, andhas an annular surface opposed to the annular surface of said firstbearing body; and a synthetic resin-made annular sheet which isinterposed between the annular surfaces and slidably abuts against atleast one of said bearing bodies.
 2. The sliding bearing according toclaim 1, wherein said annular sheet is formed of a synthetic resinincluding at least one of polyamide resin, polyester resin, polyolefinresin, polycarbonate resin, and fluororesin.
 3. The sliding bearingaccording to claim 1, wherein said annular sheet has a thickness of from0.05 mm to 1.0 mm.
 4. The sliding bearing according to claim 1, whereinboth of said bearing bodies are formed of a synthetic resin.
 5. Thesliding bearing according to claim 1, wherein both of said bearingbodies are formed of a synthetic resin including at least one ofpolyacetal resin, polyamide resin, polyester resin, polyolefin resin,polycarbonate resin, and fluororesin.
 6. The sliding bearing accordingto claim 1, wherein said first bearing body is formed of polyacetalresin, and said second bearing body is formed of a synthetic resinincluding at least one of polyacetal resin, polyamide resin, polyolefinresin, and fluororesin.
 7. The sliding bearing according to claim 1,wherein said first bearing body at a radially outer peripheral edgeportion thereof is adapted to be resiliently fitted to said secondbearing body at a radially outer peripheral edge portion of said secondbearing body.
 8. The sliding bearing according to claim 1, wherein alabyrinth is formed between said bearing bodies in at least one of theouter peripheral edge portions and inner peripheral edge portions, asviewed in a radial direction, of both of said bearing bodies.
 9. Thesliding bearing according to claim 1, wherein said second bearing bodyhas a projection formed integrally on the annular surface thereof, andsaid sheet is interposed between said projection and the annular surfaceof said first bearing body and slidably abuts against at least one ofsaid projection and the annular surface of said first bearing body. 10.The sliding bearing according to claim 9, wherein a closed recesssurrounded by said projection is formed on the annular surface of saidsecond bearing body, and a fluid is adapted to be filled in at least oneof said closed recess and an annular closed space formed between saidannular sheet and the annular surface of said first bearing body andcorresponding to said closed recess.
 11. The sliding bearing accordingto claim 10, wherein the fluid filled in at least one of said closedrecess and said closed space is adapted to receive a thrust load. 12.The sliding bearing according to claim 10, wherein said projection isadapted to be flexurally deformed under a thrust load so as to makesmall one of a fluid filling capacity of said closed recess and a fluidfilling capacity of said closed space.
 13. The sliding bearing accordingto claim 10, wherein said projection is adapted to be flexurallydeformed under a thrust load so as to cause the fluid in at least one ofsaid closed recess and said closed space to generate internal pressureby making small at least one of the fluid filling capacity of saidclosed recess and the fluid filling capacity of said closed space. 14.The sliding bearing according to claim 10, wherein the fluid includes atleast one of grease and lubricating oil.
 15. The sliding bearingaccording to claim 10, wherein the fluid is constituted bysilicone-based grease.
 16. The sliding bearing according to claim 9,wherein said projection includes at least an inner annular projectiondisposed on an inner peripheral side and an outer annular projectiondisposed radially outwardly of and substantially concentrically withsaid inner annular projection.
 17. The sliding bearing according toclaim 9, wherein said projection includes at least an inner annularprojection disposed on an inner peripheral side, an outer annularprojection disposed radially outwardly of and substantiallyconcentrically with said inner annular projection, and a radialprotrusion extending radially and connected integrally to respectiveones of said inner annular projection and said outer annular projection.18. The sliding bearing according to claim 16, wherein said projectionfurther includes at least one intermediate annular projection disposedbetween and substantially concentrically with said inner annularprojection and said outer annular projection, as viewed in the radialdirection.
 19. The sliding bearing according to claim 9, wherein saidsecond bearing body includes a bearing member and an annular piecedisposed between said bearing member and said first bearing body so asto be rotatable about the axis of said first bearing body with respectto at least one of said first bearing body and said bearing member, andsaid annular piece has said annular surface opposing the syntheticresin-made annular surface of said first bearing body as well as saidprojection formed integrally on said annular surface.
 20. The slidingbearing according to claim 19, wherein said bearing member is formed ofpolyacetal resin, and said annular piece is formed of a synthetic resinincluding at least one of polyamide resin, polyolefin resin, andfluororesin. 21-37. (canceled)